An entity, such as an organization, corporation, or governmental entity, may have a number of IP addresses allocated to it through which computers may be used for internal and external communication. For some entities, employees at different locations may communicate with each other using different network service providers, such as Internet Service Providers (ISPs). Some entities may also be accessed using third-party hosting providers and virtualized cloud services, which often assign part of their own allocated IP addresses to the entity instead of one of the IP addresses already allocated to the entity. As a result, an entity may not know each of the different IP addresses through which employees and computers of the entity communicate.